System and method for testing electrosurgical generators

ABSTRACT

A system is provided. The system includes an electrosurgical generator configured to measure, collect and record data pertaining to a characteristic of tissue as the tissue is being electrosurgically treated. A tuner configured to couple to the electrosurgical generator includes a tuning circuit providing a load having a variable complex impedance for the electrosurgical generator when the electrosurgical generator is connected thereto. A controller including stored data pertaining to impedance values is in operable communication with the electrosurgical generator for retrieving the recorded data pertaining to the characteristic of tissue. The controller is in operable communication with the tuner for varying a complex impedance of the load. The controller configured to compare the recorded data pertaining to the at least one characteristic of tissue with the stored data pertaining to the plurality of impedance values and to adjust the tuner to one of the plurality of impedance values.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation application of U.S. patentapplication Ser. No. 14/923,959, filed Oct. 27, 2015, now U.S. Pat. No.9,763,726, which is a continuation application of U.S. patentapplication Ser. No. 13/889,517 filed on May 8, 2013, now U.S. Pat. No.9,192,425, which claims the benefit of and priority to U.S. ProvisionalApplication Ser. No. 61/664,547, filed on Jun. 26, 2012, the entiredisclosures of all of which are incorporated herein by reference.

BACKGROUND Technical Field

The present disclosure relates to systems and methods for testingelectrosurgical generators. More particularly, the present disclosurerelates to systems and methods including a controller, tuner and stepmotor configured to simulate an electrosurgical procedure for testingelectrosurgical generators to support a variety of developmental andresearch activities associated therewith.

Description of Related Art

Electrosurgical generators that are utilized in conjunction with one ormore types of electrosurgical instruments to electrosurgically treattissue are well known in the art. For example, and in one particularinstance, the electrosurgical generator and instrument may be configuredto seal tissue. As is known in the art, sealing tissue, typically,includes (in the broadest sense) the steps of grasping tissue with jawmembers associated with the electrosurgical instrument and providingelectrosurgical energy to the grasped tissue to seal the tissue. Tocreate an effective tissue seal, a specific gap distance (e.g., in therange from about 0.001 inches to about 0.006) needs to be maintainedbetween the jaw members during the sealing process. In addition, aspecific pressure (e.g., in the range from about 3 kg/cm² to about 16kg/cm²) needs to be maintained on tissue during the sealing process.Moreover, one or more controllers are associated with theelectrosurgical generator and are configured to control the amount ofelectrosurgical energy that is provided to the jaw members during thesealing cycle. All of these three factors contribute in providing aneffective, uniform and consistent tissue seal. In certain instances,after the tissue is sealed, one or more suitable devices may be utilizedto sever the sealed tissue.

During the sealing process, characteristics of tissue, e.g., impedanceof tissue, change due to the fact that the tissue is being heated,desiccated fused and dehydrated. In particular, goes through this cycle,the tissue impedance characteristics change which, in turn, cause thereal and imaginary parts of the impedance to behave differently. Mostelectrosurgical generators are equipped to handle these changes inimpedance such that tissue can be effectively sealed. In particular, oneor more control algorithms, sensors, etc., in operable communicationwith the electrosurgical generator are, typically, configured to monitorand compensate for these changes in impedance during the sealing cycles.

Electrosurgical generators may be tested prior to use to ensure that theelectrosurgical generator and operable components associated therewithwill function as intended during an electrosurgical procedure. As isconventional in the art, to test the electrosurgical generators, asealing phase may be simulated utilizing a range of resistors with fixedvalues that are placed on an output of the electrosurgical generator.The fixed resistors are configured to represent tissue that is to besealed. With the resistors in place at the output of the electrosurgicalenergy, the electrosurgical generator may be run through a simulatedsealing cycle and relevant data pertaining to the sealing simulation maybe collected. As can be appreciated, this testing method only providesdata that pertains to “purely” resistive loads. As noted above, however,tissue impedance includes both real and imaginary parts, which behavedifferently. Accordingly, the aforementioned testing method may notprovide an accurate or complete representation of the changes in tissueimpedance as the tissue is being sealed.

SUMMARY

In view of the foregoing, systems and methods including a controller,tuner and step motor configured to simulate an electrosurgical procedurefor testing electrosurgical generators to support a variety ofdevelopment activities associated therewith may prove useful in themedical field.

Embodiments of the present disclosure are described in detail withreference to the drawing figures wherein like reference numeralsidentify similar or identical elements. As used herein, the term“distal” refers to the portion that is being described which is furtherfrom a user, while the term “proximal” refers to the portion that isbeing described which is closer to a user.

An aspect of the present disclosure provides a system. The systemincludes an external measurement device that is configured to measure,collect and record data pertaining to at least one characteristic oftissue as the tissue is being electrosurgically treated. A tuner isconfigured to couple to an electrosurgical generator and includes atleast one tuning circuit that is configured to provide a load having avariable complex impedance for the electrosurgical generator when theelectrosurgical generator is coupled to the tuner. A controller isconfigured to couple to the electrosurgical generator for diagnostictesting thereof. The controller includes stored data pertaining to aplurality of impedance values. The controller is in operablecommunication with the external measurement device for retrieving therecorded data pertaining to the at least one characteristic of tissueand in operable communication with the tuner for varying a compleximpedance of the load. The controller is configured to compare therecorded data pertaining to the at least one characteristic of tissuewith the stored data pertaining to the plurality of impedance values andto adjust the tuner to at least one of the plurality of impedance valuesduring diagnostic testing of the electrosurgical generator.

A step motor may be configured to operably couple to the controller andtuner. In this instance, the controller may be configured to activatethe step motor for varying the complex impedance of the load.

An impedance analyzer may be configured to operably couple to thecontroller and tuner when the controller and tuner are not coupled tothe electrosurgical generator or the external measurement device. Inthis instance, the impedance analyzer may be configured to measure thecomplex impedance of the load as the step motor varies the compleximpedance of the load. Moreover, the measured complex impedances of theload may be stored in the controller as the data pertaining to theplurality of impedance values.

The tuner may be, but is not limited to a passive tuner, a highfrequency tuner, a microwave tuner, a solid state tuner and an activetuner. In the particular instance where the tuner is a passive tuner, itincludes a variable Pi network having a first variable capacitorconnected in parallel with one or more variable inductors that isconnected in parallel with a second variable capacitor that is connectedin parallel with one or more resistors. Each of the first and secondvariable capacitors may include a capacitance that can vary from about40 pF to about 2,000 pF and the inductor(s) may include an inductancethat can vary from about 50 uH to about 200 uH.

An aspect of the present disclosure provides a method for testingelectrosurgical generators. An external measurement device configured tomeasure, collect and record data pertaining to at least onecharacteristic of tissue as the tissue is being electrosurgicallytreated is provided. An electrosurgical generator is coupled to a tunerincluding at least one tuning circuit configured to provide a loadhaving a variable complex impedance for the electrosurgical generatorwhen the electrosurgical generator is coupled to the tuner. The externalmeasurement device is coupled to a controller for retrieving therecorded data pertaining to the at least one characteristic of tissue.The controller is coupled to the electrosurgical generator to perform adiagnostic test thereof. The controller includes stored data pertainingto a plurality of impedance values. The controller is coupled to thetuner for varying a complex impedance of the load. The recorded datapertaining to the at least one characteristic of tissue is compared withthe stored data pertaining to the plurality of impedance values. Thetuner is adjusted to at least one of the plurality of impedance valuesduring diagnostic testing of the electrosurgical generator.

The method may include providing the external measurement device as acomponent of the electrosurgical generator.

A step motor may be provided and configured to operably couple to thecontroller and tuner. In this instance, the step motor may be activatedfor varying the complex impedance of the load.

An impedance analyzer may be provided and configured to operably coupleto the controller and tuner when the controller and tuner are notcoupled to the electrosurgical generator or the external measurementdevice. In this instance, the complex impedance of the load may bemeasured with the impedance analyzer as the step motor varies thecomplex impedance of the load.

The measured complex impedances of the load may be stored in thecontroller as the data pertaining to the plurality of impedance values.In addition, step positions of the step motor may be stored in thecontroller. The step positions correspond to the measured compleximpedances of the load.

The tuner may be, but is not limited to a passive tuner, a highfrequency tuner, a microwave tuner, a solid state tuner and an activetuner. In the particular instance where the tuner is a passive tuner, itincludes a variable Pi network having a first variable capacitorconnected in parallel with one or more variable inductors that isconnected in parallel with a second variable capacitor that is connectedin parallel with one or more resistors. Each of the first and secondvariable capacitors may include a capacitance that can vary from about40 pF to about 2,000 pF and the inductor(s) may include an inductancethat can vary from about 50 uH to about 200 uH.

An aspect of the present disclosure provides a system for testingelectrosurgical generators. The system includes an electrosurgicalgenerator that is configured to provide electrosurgical energy forelectrosurgically treating tissue and to measure, collect and recorddata pertaining to at least one characteristic of tissue as the tissueis being electrosurgically treated. A tuner is configured to couple tothe electrosurgical generator and includes at least one tuning circuitincluding a load including at least three reactive components and atleast one resistor. The tuning circuit provides a load having variablecomplex impedance for the electrosurgical generator when theelectrosurgical generator is coupled to the tuner. A controller includesstored data pertaining to a plurality of impedance values. Thecontroller is configured to couple to the electrosurgical generator fordiagnostic testing thereof and for retrieving the recorded datapertaining to the at least one characteristic of tissue. The controlleris configured to couple to a step motor that is configured to couple tothe tuner for varying at least one of the at least three reactivecomponents to vary a complex impedance of the load of the tuner. Thecontroller is configured to compare the recorded data pertaining to theat least one characteristic of tissue with the stored data pertaining tothe plurality of impedance values and to adjust the tuner to at leastone of the plurality of impedance values.

An impedance analyzer may be configured to operably couple to thecontroller and tuner when the controller and tuner are not coupled tothe electrosurgical generator. In this instance, the impedance analyzermay be configured to measure the complex impedance of the load as thestep motor varies the complex impedance of the load. The measuredcomplex impedances of the load may be stored in the controller as thedata pertaining to the plurality of impedance values.

The reactive components may include a first variable capacitor connectedin parallel with one or more variable inductors that are connected inparallel with a second variable capacitor that is connected in parallelwith one or more resistors. Each of the first and second variablecapacitors may include a capacitance that can vary from about 40 pF toabout 2,000 pF and the inductor(s) may include an inductance that canvary from about 50 uH to about 200 uH.

BRIEF DESCRIPTION OF THE DRAWING

Various embodiments of the present disclosure are described hereinbelowwith references to the drawings, wherein:

FIG. 1 is a schematic block diagram of a system utilized for testingelectrosurgical generators according to an embodiment of the instantdisclosure;

FIG. 2 is a schematic view of a passive tuner configured for use withthe system depicted in FIG. 1;

FIG. 3 is a schematic view of a high frequency tuner configured for usewith the system depicted in FIG. 1;

FIG. 4 is a schematic view of a microwave tuner configured for use withthe system depicted in FIG. 1;

FIG. 5 is a schematic view of a solid state tuner configured for usewith the system depicted in FIG. 1;

FIG. 6 is a schematic view of an active tuner configured for use withthe system depicted in FIG. 1;

FIG. 7 is schematic block diagram of a sub-system of the system depictedin FIG. 1 utilized for mapping one of the tuners depicted with thesystem depicted in FIGS. 2-6; and

FIG. 8 is schematic block diagram of a sub-system of the system depictedin FIG. 1 utilized for recording tissue during an electrosurgicalprocedure.

DETAILED DESCRIPTION

Detailed embodiments of the present disclosure are disclosed herein;however, the disclosed embodiments are merely examples of thedisclosure, which may be embodied in various forms. Therefore, specificstructural and functional details disclosed herein are not to beinterpreted as limiting, but merely as a basis for the claims and as arepresentative basis for teaching one skilled in the art to variouslyemploy the present disclosure in virtually any appropriately detailedstructure.

A system in accordance with the instant disclosure can be used tosupport a variety of developmental and research activities of anelectrosurgical generator. The system utilizes voltage, current andphase parameters obtained at a surgical site during an electrosurgicalprocedure. These parameters can be reproduced and simulated during benchtop testing to support, without limit to, algorithm development, designverification, software validation, reliability and manufacturing testingof electrosurgical generators. In addition, efficiency gains associatedwith electrosurgical generators can also be realized through automatedtesting using the system of the instant disclosure.

With reference to FIG. 1, a system 2 for testing electrosurgicalgenerators is illustrated. System 2 includes an external measurementdevice 3, a controller 6 and one or more tuners 8.

In accordance with the instant disclosure, the external measurementdevice 3 may be any suitable measurement device known in the art. Asused herein, the measurement device 3 is configured to measure, collect,calculate and record one or more electrical parameters at a surgicalsite to determine an impedance of tissue as the tissue is beingelectrosurgically treated. Suitable measurement devices 3 may includewithout limitation spectrum analyzers, oscilloscopes, and the like. Forthe purposes herein, however, it is assumed that a generator 4 includesa measurement device 3 therein that is configured to measure, collect,calculate and record one or more electrical parameters at a surgicalsite to determine an impedance of tissue as the tissue is beingelectrosurgically treated (FIG. 1). Alternatively, the measurementdevice 3 may be configured to selectively couple to the generator 4.

Continuing with reference to FIG. 1, generator 4 includes suitable inputcontrols (e.g., buttons, activators, switches, touch screen, etc.) forcontrolling the generator 4. The controls allow a user to adjust powerof the RF energy, waveform parameters (e.g., crest factor, duty cycle,etc.), and other parameters to achieve the desired waveform suitable fora particular task (e.g., coagulating, tissue sealing, intensity setting,etc.).

Generator 4 includes a DC power supply 10 that is connected to aconventional AC source (e.g., electrical wall outlet) and includes a lowvoltage power supply 12 (“LVPS”) and a high voltage power supply 14(“HVPS”) (FIG. 1). The HVPS 14 provides high voltage DC power to an RFoutput stage 16, e.g., an RF amp module, which then converts highvoltage DC power into RF energy and delivers the RF energy to the activeterminal 18. The energy is returned thereto via the return terminal 20.The LVPS 12 provides power to various components of the generator 4(e.g., measurement device 3, input controls, displays, etc.). Thegenerator 4 may include a plurality of connectors to accommodate varioustypes of devices (e.g., an electrosurgical instrument, controller,tuner, external measurement device 3, etc.).

Generator 4 further includes a microcontroller 22 including amicroprocessor 24 operably connected to a memory 26, which may bevolatile type memory (e.g., RAM) and/or non-volatile type memory (e.g.,flash media, disk media, etc.) (FIG. 1). The microcontroller 22 includesan output port that is operably connected to the DC power supply 10and/or RF output stage 16 allowing the microprocessor 24 to control theoutput of the generator 4 according to either open and/or closed controlloop schemes. Those skilled in the art will appreciate that themicroprocessor 24 may be substituted by any logic processor (e.g.,control circuit) adapted to perform the calculations discussed herein.

Generator 4 may be in operable communication with one or more sensors(not shown) that are configured to provide characteristic informationpertaining to tissue as the tissue is being electrosurgically treated.The characteristic information pertaining to tissue may be communicatedto the microcontroller 22 for processing by the microprocessor 24 andsubsequent storage into memory 26.

In accordance with the instant disclosure, the generator 4 is configuredto provide electrosurgical energy for electrosurgically treating tissue,see FIG. 8 for example. As noted above, generator 4 is also configuredto measure, collect and record data pertaining to one or morecharacteristics of tissue, e.g., impedance of tissue, as the tissue isbeing electrosurgically treated. One or more electrical parameters,e.g., voltage, current, power, phase, etc. may be taken at the tissuesite to calculate the impedance of tissue. This data pertaining to theimpedance of tissue is stored in memory 26 and is accessible bycontroller 6 for future use thereof. In particular, the calculatedtissue impedances are mapped to a Smith Chart by suitable methods andutilized by the controller 6 to manipulate the tuner 8 to match thecalculated tissue impedances and vary an impedance of a load “L” of thetuner 8 with respect to time (as is described in greater detail below).As can be appreciated, this mapping to the Smith Chart can be done for aparticular electrosurgical instrument utilized with the generator 4,electrosurgical procedure, tissue type, etc.

With continued reference to FIG. 1, controller 6 includes one or moremicroprocessors 30 operably connected to a memory 32, which may bevolatile type memory (e.g., RAM) and/or non-volatile type memory (e.g.,flash media, disk media, etc.). Those skilled in the art will appreciatethat the microprocessor 30 may be substituted by any logic processor(e.g., control circuit) adapted to perform the calculations discussedherein. The controller 6 includes input and output ports 36 and 38,respectively, which allow the controller 6 to communicate with one ormore components, e.g., generator 4, tuner 8, step motor 50, impedanceanalyzer 52, etc., of the system 2 (FIG. 1).

Controller 6 includes stored data that pertains to a plurality ofimpedance values. The plurality of impedance values are obtained bymapping passive components of the tuner 8 to a Smith Chart. Tuner 8 maybe any suitable type of tuner including but not limited to thosedescribed in FIGS. 2-6.

FIG. 2 illustrates an RF tuner, e.g., a passive tuner 8 a. The passivetuner 8 a includes a variable Pi network having a first variablecapacitor C1 connected in parallel with one or more variable inductorsL1 that is connected in parallel with a second variable capacitor C2that is connected in parallel with one or more resistors R1. Each of thefirst and second variable capacitors C1 and C2 include a capacitancethat can vary from about 40 pF to about 2,000 pF and the inductor(s) mayinclude an inductance that can vary from about 50 uH to about 200 uH. Anadvantage of a Pi network is that it covers an entire range of the SmithChart with a minimal amount of passive components.

FIG. 3 illustrates a high frequency tuner 8 b. Unlike the passive tuner8 a, however, high frequency tuner 8 b does not cover the entire rangeof the Smith Chart. This type of tuner is suitable for testing thegenerator 4 when the generator 4 is configured to transmitelectrosurgical energy in the high frequency range, e.g., Megahertzfrequency range. One advantage of the high frequency tuner 8 b is thatit utilizes only three passive components, a capacitor C3, an inductorL2 and a resistor R2. To increase coverage around the Smith Chartwithout adding more passive components, an optional quarter wavelengthof cable 40 may be positioned between the generator 4 and the tuner 8 b;this functions to shift an impedance 180° around the Smith Chart.

FIG. 4 illustrates a microwave tuner 8 c. This type of tuner is suitablefor testing the generator 4 when the generator 4 is configured totransmit electrosurgical energy in the microwave frequency range. Inthis particular embodiment, an adjustable tuning stub 42 that isconnected to ground can be either an open or a short circuit node andmay vary in length as dictated by controller 6. In certain embodiments,the tuning stub 42 can be moved towards or away from the load to shiftthe load around the Smith Chart. The location of the adjustable stub 42shifts the load around the Smith Chart by placing the adjustable stub inparallel with the load. The microwave tuner 8 b is relatively small whencompared to the aforementioned tuners (or tuners yet to be described).

FIG. 5 illustrates a solid state tuner 8 d. Solid state tuner 8 d usesone or more pin diodes (two pin diodes 44 a-44 b illustrated) to“switch-in” respective tuning capacitors C4, C5 (which are connected toground) and various taps on an inductor L3. Solid state tuner 8 dincludes a resistor R3 that is connected to ground. In the embodimentillustrated in FIG. 5, a bias line 46 is utilized to turn on and off thediodes 44 a-44 b and is isolated from the RF frequencies by a chokeinductor L4 and a bypass capacitor C6. The bias line 46 includes a diodeD1 in series with a capacitor C7 that is connected to ground. Anadvantage of the tuner 8 d is that is has no mechanical parts and canhave higher repeatability and reliability when compared to other tuners,e.g., tuner 8 a.

FIG. 6 illustrates an active tuner 8 e that utilizes a FET 48 (or othersuitable device) to increase or decrease a load of the active tuner 8 e.In this instance, the controller 6 can adjust a gate voltage Vg, whichadjusts an on resistance of the FET 48 which, in turn, increases and/ordecreases the overall resistance of the active tuner 8 e. Active tuner 8e includes a very fast response time and, in some instances, may be ableto simulate an arcing event. An advantage of the tuner 8 e when comparedto the aforementioned tuners is that tuner 8 e does not require mappingto a Smith Chart, i.e., the load of the tuner 8 e is monitored usingvoltage and current.

With reference to FIG. 7, a step motor 50 is configured to operablycouple to the controller 6 and one or more of the tuners 8 (forillustrative purposes, step motor 50 is described in terms of use withthe passive tuner 8 a) to control the tuner 8 a to a specific impedance.Positions of the step motor 50 are utilized to vary one or more of thepassive components in the tuner 8 a and are then mapped to acorresponding value on the Smith Chart. In particular, step motor 50 isconfigured to couple to the tuner 8 a to vary one or more of the firstand second capacitors C1-C2, inductors L1 and/or resistor R1. Thepositions of the step motor 50 are then mapped to a corresponding valueon the Smith Chart to control the tuner 8 a to a specific impedance. Toaccomplish this, controller 6 is utilized to control the step motor 50as the step motor 50 moves through each of the positions of the stepmotor 50 and measures an impedance value, e.g., complex impedance, ofthe load of the tuner 8 a.

With continued reference to FIG. 7, an impedance analyzer 52 isconfigured to operably couple to the controller 6 and one or more of thetuners 8, e.g., tuner 8 a. The impedance analyzer 52 is configured tomeasure the complex impedance of the load of the tuner 8 a as the stepmotor 50 varies the complex impedance of the load. The measured compleximpedances of the load and motor positions of the step motor 50 arestored in memory 32 of the controller 6.

Controller 6 is configured to operably couple to the generator 4 forretrieving the recorded data pertaining to the characteristic(s) oftissue, e.g., calculated tissue impedances that were previously mappedto the Smith Chart. Controller 6 is configured to compare the recordeddata pertaining to the characteristic(s) of tissue with stored datapertaining to the plurality of impedance values that were previouslyobtained with the use of one of the tuners 8, e.g., tuner 8 a and basedon this comparison, the controller 6 adjusts a load of the tuner 8 toone or more of the plurality of impedance values. In particular, in adiagnostic testing or simulation sequence, the tuner 8 functions as aload “L” for an output of the generator 4 and an impedance of the load“L” of the tuner 8 may be varied by varying one or more of the passivecomponents of the tuner 8.

Operation of the system 2 is described in terms of testing generator 4for possible instabilities that may be associated with the generator 4after and/or prior to use thereof.

For purposes herein, it is assumed that calculated impedance values havebeen previously obtained during an electrosurgical procedure, mapped toa Smith Chart and stored into memory 26 of generator 4.

Generator 4 may be coupled to the controller 6 and one or more of theaforementioned tuners 8, e.g., passive tuner 8 a. Controller 6 downloadsthe calculated impedance values from the generator 4. In the illustratedembodiment, generator 4 was utilized to obtain the calculatedimpedances. Alternately, the external measurement device 3 may have beenused to collect, record, calculate and, subsequently, store theimpedance values into memory 26 of the generator 4. Controller 6compares the calculated impedance values with known impedance valuesincluding corresponding step positions of the step motor 50 stored inmemory 32.

With generator 4 coupled to the tuner 8 a, generator 4 is activated torun through a simulated tissue sealing phase. Controller 6 activates thestep motor 50 to move the step motor 50 to vary the inductance of theinductor L1 and/or capacitance of the first and second capacitors C1-C2to vary the complex impedance of the tuner 8 a. Varying the compleximpedance of the tuner 8 a around the Smith Chart “mimics” actual tissueresponse. The controller 6 can move through as many positions of thestep motor 50 as needed to check for possible instabilities that may beassociated with the generator 4.

As can be appreciated, the aforementioned system 2 overcomes theaforementioned drawbacks typically associated with conventional methodsthat are utilized to test electrosurgical generators. That is, system 2tests the generator 4 through a tissue simulation that utilizes bothreal and imaginary parts of impedance and not just the real part as isutilized by conventional testing methods.

From the foregoing and with reference to the various figure drawings,those skilled in the art will appreciate that certain modifications canalso be made to the present disclosure without departing from the scopeof the same. For example, the system 2 may be utilized to supportverification and validation of a specific design of a generator. Or, incertain instances, the system 2 may be utilized for realizing efficiencygains. Those skilled in the art will realize that the system 2 may beutilized to provide a host of other benefits not described herein.

While the Smith Chart has been described herein as representingimpedances, the Smith Chart may be used to represent other parametersincluding, but not limited to, admittances, reflection coefficients,scattering parameters, noise figure circles, constant gain contours andregions for unconditional stability.

While several embodiments of the disclosure have been shown in thedrawings, it is not intended that the disclosure be limited thereto, asit is intended that the disclosure be as broad in scope as the art willallow and that the specification be read likewise. Therefore, the abovedescription should not be construed as limiting, but merely asexemplifications of particular embodiments. Those skilled in the artwill envision other modifications within the scope and spirit of theclaims appended hereto.

1-20. (canceled)
 21. A system, comprising: an electrosurgical generatorconfigured to output energy and including an active terminal and areturn terminal; a tuner configured to couple to the active terminal andthe return terminal to complete a circuit and to provide a simulatedtissue load having a variable complex impedance for the electrosurgicalgenerator; and a controller coupled to the electrosurgical generator andthe tuner, the controller configured to vary the variable compleximpedance of the tuner.
 22. The system according to claim 21, furthercomprising a step motor coupled to the controller and the tuner, thecontroller configured to activate the step motor to vary the variablecomplex impedance of the tuner.
 23. The system according to claim 22,further comprising an impedance analyzer operably coupled to thecontroller and the tuner, the impedance analyzer configured to measurethe variable complex impedance of the tuner as the step motor varies thevariable complex impedance of the tuner, wherein measured variablecomplex impedances of the tuner are stored in the controller as datapertaining to a plurality of complex impedance values.
 24. The systemaccording to claim 21, wherein the tuner is selected from the groupconsisting of a passive tuner, a high frequency tuner, a microwavetuner, a solid state tuner, and an active tuner.
 25. The systemaccording to claim 21, wherein the tuner is a passive tuner including avariable Pi network having a first variable capacitor connected inparallel with a variable inductor that is connected in parallel with asecond variable capacitor that is connected in parallel with a resistor.26. The system according to claim 25, wherein each of the first variablecapacitor and the second variable capacitor includes a variablecapacitance from 40 pF to 2,000 pF and the variable inductor includes avariable inductance from 50 uH to 200 uH.
 27. A method for testing anelectrosurgical generator, comprising: coupling a tuner to an active anda return terminal of an RF output stage of an electrosurgical generatorto complete a circuit with the RF output stage, the tuner configured toprovide a simulated tissue load having a variable complex impedance tothe electrosurgical generator; coupling a controller to the tuner and tothe electrosurgical generator, the controller configured to vary thevariable complex impedance of the tuner; and performing a diagnostictest on the electrosurgical generator by operating the electrosurgicalgenerator and varying the variable complex impedance of the tuner viathe controller.
 28. The method according to claim 27, further comprisingcontrolling a step motor coupled to the controller and the tuner to varythe variable complex impedance of the tuner.
 29. The method according toclaim 28, further comprising coupling an impedance analyzer to thecontroller and the tuner.
 30. The method according to claim 29, furthercomprising measuring the variable complex impedance of the tuner withthe impedance analyzer as the step motor varies the variable compleximpedance of the tuner.
 31. The method according to claim 30, furthercomprising storing step positions of the step motor in the controller,the step positions corresponding to measured variable complex impedancesof the tuner.
 32. The method according to claim 27, wherein the tuner isselected from the group consisting of a passive tuner, a high frequencytuner, a microwave tuner, a solid state tuner, and an active tuner. 33.The method according to claim 27, wherein the tuner is a passive tunerincluding a variable Pi network having a first variable capacitorconnected in parallel with a variable inductor that is connected inparallel with a second variable capacitor that is connected in parallelwith a resistor.
 34. The method according to claim 33, wherein each ofthe first variable capacitor and the second variable capacitor includesa variable capacitance from 40 pF to 2,000 pF and the inductor includesa variable inductance from 50 uH to 200 uH.